The White Cliffs of Dover, part of the North Downs formation, is the name given to the region of English coastline facing the Strait of Dover and France. The cliff face, which reaches a height of 350 feet (110 m), owes its striking appearance to its composition of chalk accented by streaks of black flint. The cliffs, on both sides of the town of Dover in Kent, stretch for eight miles (13 km). A section of coastline encompassing the cliffs was purchased by the National Trust in 2016.[1]

About 70 million years ago Great Britain and much of Europe was submerged under a great sea. The sea bottom was covered with white mud formed from fragments of coccoliths, the skeletons of tiny algae that floated in the surface waters and sank to the bottom during the Cretaceous period and, together with the remains of bottom-living creatures, formed muddy sediments. It is thought that the sediments were deposited very slowly, probably half a millimetre a year, equivalent to about 180 coccoliths piled one on top of another. Up to 1,600 feet (500 m) 500 metres of sediments were deposited in some areas.[6] The weight of overlying sediments caused the deposits to became consolidated into chalk.[7]

The cliffs' multiple layers of flint match those seen across the channel at Cap Gris Nez, France, evidence of a land connection between England and France in prehistoric times.

Subsequent earth movements related to the formation of the Alps raised the sea-floor deposits above sea level. Until the end of the last glacial period, the British Isles were part of continental Europe, linked by the unbroken Weald-Artois Anticline, a ridge that acted as a natural dam to hold back a large freshwater pro-glacial lake, now submerged under the North Sea. The land masses remained connected until between 450,000 and 180,000 years ago when at least two catastrophic glacial lake outburst floods breached the anticline and destroyed the ridge that connected Britain to Europe. A land connection across the southern North Sea existed intermittently at later times when periods of glaciation resulted in lower sea levels.[8] At the end of the last glacial period, around 10,000 years ago, rising sea levels finally severed the last land connection.[9]

Evidence of erosion along the cliff top

The cliffs' chalk face shows horizontal bands of dark-coloured flint which is composed of the remains of sea sponges and siliceous planktonic micro-organisms which hardened into the microscopic quartz crystals. Quartz silica filled cavities left by dead marine creatures which are found as flint fossils, especially the internal moulds of Micraster echinoids. Several different ocean floor species such as brachiopods, bivalves, crinoids, and sponges be can found in the chalk deposits, as can sharks' teeth.[10]

In some areas, layers of a soft, grey chalk known as a hardground complex can be seen. Hardgrounds are thought to reflect disruptions in the steady accumulation of sediment when sedimentation ceased and/or the loose surface sediments were stripped away by currents or slumping, exposing the older hardened chalk sediment. A single hardground may have been exhumed 16 or more times before the sediments were compacted and hardened (lithified) to form chalk.[10]

The cliff face continues to weather at an average rate of 1 centimetre (0.4 in) per year, although occasionally large pieces will fall. In 2001, a large chunk of the cliff edge, as large as a football pitch, fell into the Channel.[11] Another large section collapsed on 15 March 2012.[12]

The chalk grassland environment above the cliffs provides an excellent environment for many species of wild flowers, butterflies and birds, and has been designated a Special Area of Conservation and a Site of Special Scientific Interest. Rangers and volunteers work to clear invasive plants that threaten the native flora. A grazing programme involving Exmoor ponies has been established to help to clear faster-growing invasive plants, allowing smaller, less robust native plants to survive.[13] The ponies are managed by the National Trust, Natural England, and County Wildlife Trusts to maintain vegetation on nature reserves.[14]

Peregrine falcon off White Cliffs, Dover

The cliffs are the first landing point for many migratory birds flying inland from across the English Channel. After a 120-year absence, in 2009 it was reported that ravens had returned to the cliffs. Similar in appearance but smaller, the jackdaw is abundant. The rarest of the birds that live along the cliffs is the peregrine falcon. In recent decline and endangered, the skylark also makes its home on the cliffs.[15] The cliffs are home to fulmars, which resemble gulls, and to colonies of black-legged kittiwake, a species of gull. Bluebird, as mentioned in the classic World War II song "(There'll Be Bluebirds Over) The White Cliffs of Dover" is an old country name for swallows and house martins, which make an annual migration to continental Europe, many of them crossing the English Channel at least twice a year.

Among the wildflowers are several varieties of orchids, the rarest of which is the early spider orchid, which has yellow-green to brownish green petals and looks like the body of a large spider. The oxtongue broomrape is an unusual plant that lives on the roots of a host plant. It has yellow, white, or blue snapdragon-like flowers and about 90 per cent of the UK's population is found on the cliffs.
Viper's-bugloss, a showy plant in vivid shades of blue and purple with red stamens, also grows along the cliffs.[15] In his play King Lear, Shakespeare mentions rock samphire, an edible plant that grows on the cliffs. It was collected by gatherers who hung from ropes down the cliff: "Half-way down / Hangs one that gathers samphire; dreadful trade!" (Act IV, Scene VI). This refers to the dangers involved in collecting rock samphire on sea cliffs.

The abundance of wildflowers provides homes for about thirty species of butterfly. The rare Adonis blue can be seen in spring and again in autumn. Males have vibrant blue wings lined with a white margin, whereas the females are a rich chocolate brown. This species' sole larval food plant is the horseshoe vetch and it has a symbiotic relationship with red or black ants. The eggs are laid singly on very small foodplants growing in short turf. This provides a warm microclimate, suitable for larval development, which is also favoured by ants. The caterpillar has green and yellow stripes to provide camouflage while it feeds on vetch. The ants milk the sugary secretions from the larval "honey glands" and, in return, protect the larvae from predators and parasitoids, even going so far as to bury them at night. The larvae pupate in the upper soil, and continue to be protected by the ants, often in their nests, until the adults emerge in the spring or autumn.[16]

Samphire Hoe Country Park is a nature reserve on a new piece of land created by the earth excavated during the construction of the Channel Tunnel. It covers a 74-acre (30 ha) site at the foot of Shakespeare Cliff, between Dover and Folkestone. There is an education shelter with a classroom and exhibition area. Staff and volunteers are available to answer questions and provide information about the wildlife in the reserve. The building's design incorporates eco-construction criteria. Samphire, a wild edible plant, grew on the cliffs and was gathered by hanging from ropes over the cliff's edge. Shakespeare Cliff was named after the reference to this in Shakespeare's play King Lear.

A possible Iron Age hillfort has been discovered at Dover, on the site of the later castle.[18] The area was also inhabited during the Roman period, when Dover was used as a port. A lighthouse survives from this era, one of a pair at Dover which helped shipping navigate the port. It is likely the area around the surviving lighthouse was inhabited in the early medieval period as archaeologists have found a Saxon cemetery here, and the church of St Mary in Castro was built next to the lighthouse in the 10th or 11th century.[19] It is thought that the Old English name for Britain, Albion, was derived from the latin albus (meaning 'white') as an allusion to the white cliffs.[20]

Dover Castle, the largest castle in England,[21] was founded in the 11th century. It has been described as the "Key to England" owing to its defensive significance throughout history.[22][23] The castle was founded by William the Conqueror in 1066 and rebuilt for Henry II, King John, and Henry III. This expanded the castle to its current size, taking its curtain walls to the edge of the cliffs. During the First Barons' War the castle was held by King John's soldiers and besieged by the French between May 1216 and May 1217. The castle was also besieged in the 1265 during the Second Barons' War. In the 16th century cannons were installed at the castle, but it became less important militarily as Henry VIII had built artillery forts along the coast. Dover Castle was captured in 1642 during the Civil War when townspeople climbed the cliffs and surprised the royalist garrison, giving a symbolic victory against royal control. Towards the end of the war many castles were slighted, but Dover was spared.[24]

The castle had renewed importance from the 1740s as the development of heavy artillery made capturing ports an important part of warfare. During the Napoleonic Wars in particular the defences were remodelled and a series of tunnels were dug into the cliff to act as barracks, adding space for an extra 2,000 soldiers. The tunnels mostly lay abandoned until the Second World War.[25]

The cliffs have great symbolic value in Britain because they face towards continental Europe across the narrowest part of the English Channel, where invasions have historically threatened and against which the cliffs form a symbolic guard. The National Trust calls the cliffs "an icon of Britain", with "the white chalk face a symbol of home and war time defence."[26] Because crossing at Dover was the primary route to the continent before the advent of air travel, the white line of cliffs also formed the first or last sight of Britain for travellers. During the Second World War, thousands of allied troops on the little ships in the Dunkirk evacuation saw the welcoming sight of the cliffs.[27] In the summer of 1940, reporters gathered at Shakespeare Cliff to watch aerial dogfights between German and British aircraft during the Battle of Britain.[28]

Vera Lynn, known as "The Forces' Sweetheart" for her 1942 wartime classic "(There'll Be Bluebirds Over) The White Cliffs of Dover" celebrated her 100th birthday in 2017. That year she led a campaign for donations to buy 170 acres (0.7 km2) of land atop Dover's cliffs when it was feared that they might be sold to developers; the campaign met its target after only three weeks. The National Trust, which owns the surrounding areas, plans to return the land to a natural state of chalk grassland and preserve existing military structures from the Second World War.[29]

Dover Museum was founded in 1836. Shelled from France in 1942 during the Second World War, the museum lost much of its collections, including nearly all its natural history collections. Much of the surviving material was left neglected in caves and other stores until 1946. In 1948 a temporary museum was opened and in 1991 a new museum of three storeys, built behind its original Victorian façade, was opened. In 1999, a new gallery on the second floor centred on the Dover Bronze Age Boat was opened.[30]

The most famous reference in English literature to the White Cliffs is in Shakespeare's King Lear, Act IV, Scene I. Edgar persuades the blinded Earl of Gloucester that he is at the edge of a cliff in Dover. Gloucester says "There is cliff, whose high and bending head looks fearfully in the confined deep: Bring me to the very brim of it." Edgar fools the Gloucester into thinking he is at the cliff edge and describes the scene: "Here's the place! - stand still - how fearful/ And dizzy 'tis, to cast one's eye so low ... half way down/Hangs one that gathers samphire: dreadful trade!/Methinks he seems no bigger than his head."[31]